In recent years, the sputtering method capable of easily controlling the film thickness and components is being widely used as one of the deposition methods of materials for electronic and electric components.
This sputtering method makes a substrate, which is formed of a positive electrode and a negative electrode, and a target face each other and applies a high voltage between such substrate and target under an inert gas atmosphere in order to generate an electric field, and employs the fundamental principle in which plasma is formed upon the atoms ionized at such time colliding with the inert gas, the positive ions within this plasma colliding with the target (negative electrode) surface and discharging the atoms structuring the target, whereby the film is formed by the discharged atoms adhering to the opposing substrate surface.
Upon forming a thin film with this sputtering method, the problem of the production of particles has been attracting attention. In terms of particles caused by the target during the sputtering method, for example, the thin film is deposited within the walls of the thin film forming device and all over the materials and the like therein, in addition to the substrate, when a target is sputtered.
Faces and side faces other than the erosion portion of the target are no exceptions, and the deposits of sputtered particles have been observed.
And, flakes separating from such materials and the like within the thin film forming device directly flying on the substrate surface is considered to be one of the major causes for the production of particles.
Recently, while the degree of integration of LSI semiconductor devices has increased (64 MB, 256 MB and even 1 GB) on the one hand, it is also becoming miniaturized with the wiring width rule being less than 0.2 μm in some cases, and problems such as the disconnection and short circuit of wiring due to the foregoing particles now occur more frequently.
As described above, the production of particles is now even a larger problem pursuant to the advancement of high integration and miniaturization of electronic device circuits.
Generally, a sputtering target is connected to a backing plate having a larger measurement with such means as welding, diffusion bonding or soldering. From the perspective of the stabilization of sputtering, however, the side face of the sputtering target to be connected to the backing plate is usually formed to have an inclined face broadening toward such backing plate.
As publicly known, a backing plate plays the role of cooling the target by the back face thereof contacting a coolant, and materials such as aluminum or copper or the alloys thereof having a favorable thermal conductivity are used.
The side face of the foregoing sputtering target is not the portion which will erode (become subject to wear) from sputtering. Nonetheless, since it is close to the erosion face of the target, there is a trend toward the sputtered particles flying during the sputtering operation further adhering and depositing thereto.
In general, the erosion face of a sputtering target has a smooth surface from the turning process, and the foregoing inclined side face is similarly subject to the turning process. Whereas, it has become known that the sputtered particles (deposits) once adhered to the inclined side face are separated therefrom once again, float, and cause the production of particles.
In light of the demands of the high integration and miniaturization of electronic device circuits as described above, and in order to overcome the foregoing problems, a proposal has been made of roughening the surface of the target, backing plate as well as the apparatus inside the sputtering device through blast processing (for example, Japanese Patent Laid-Open Publication No. H9-176843), formation of spray coating film (for example, Japanese Patent Laid-Open Publication No. H9-176842), knurling processing (for example, Japanese Patent Laid-Open Publication No. H10-330971), etching processing, electrical discharge machining (for example, Japanese Patent Laid-Open Publication No. H11-131224) and so on in order to improve the adhesiveness, and to prevent the re-separation of the deposited sputtered particles.
Nevertheless, when performing blast processing to the surface of the target, backing plate as well as the apparatus inside the sputtering device, for instance, in order to improve the adhesiveness with the anchor effect, problems such as the contamination of goods due to the remnants of the blast materials would arise. For example, beads of alumina, zirconia and SiC or the like generally used as the blast material have inferior electrical conduction, and may cause abnormal discharge by a charge-up, and the beads themselves may fall out and contaminate the goods.
Further, there is an additional problem in that the adhesiveness of the adhered particles deposited on the residual blast materials would deteriorate and would become easy to separate, and separation of the adhered film caused by the selective and uneven growth thereof would newly arise, and the fundamental issues could not be resolved.
In view of the above, the present inventors previously proposed a sputtering target producing few particles comprising a sprayed coating having a central line surface roughness of Ra 10 to 20 μm at the side face or the like of the sputtering target (Japanese Patent Application No. 2000-314778).
This technology in itself yielded an effect of preventing the separation of the adhered film and suppressing the generation of particles far superior in comparison to conventional methods. Nevertheless, in the case of such surface processing employing spray coating, there are problems in that it is difficult to control the thickness of the spray deposit, and the spray coated film may separate from the processes and contaminate the goods.
Moreover, in the case of surface roughening with knurling, there are problems in that metal contamination may occur from the knurling tools, and that device components cannot be reused since it is difficult to re-perform knurling processing to components that have already been subjected to knurling processing.
Further, in the case of roughening processing with etching, although a very rough surface can be obtained, there are problems in that the application to complex three-dimensional shapes is difficult, and that the formation of a depression angle to be a solid anchor is difficult in principle.
Meanwhile, there is a possibility that roughening processing with electrical discharge machining may mostly overcome the foregoing problems. Nevertheless, the number one problem with the roughening processing with electrical discharge machining is that the separability resistance of the deposited film with ordinary electrical discharge machining is insufficient.